Resistance device



5. RESISTANCE DEVICE Filed Fem 5, 193i EY H/S Pateiited Mar.' 13, 1934 PArENr ori-ica RESISTANCE DEVICE Q i' Samuel Ruben, New Rochelle, N. Y., assignor to Ruben Patents Company, New Rochelle, N. Y., a corporation of Delaware Application February 3 This invention relates to a resistance device andy to the method of makingit. An object of the invention is the provision of a resistance device capable of withstanding the effects of overloads and unfavorable atmospheric conditions and which lends\itself to accurate duplication in commercial production.

This invention constitutes an improvement upon my co-pending applications. filed September 17, 1928, and October 6, 1930, bearing respectively Serial Numbers 306,608, and 486,69/8. These issued as Patents 1,871,482 and 1,859,344 on Sept. 13, 1932 and May 2,4, 1932 respectively.

The resistance element of this invention consists of a base of a compound of high specific resistance, such as copper oxide and having a coating closely adherent to the surface of the base consisting' of a deilocculated graphite, the element itself consisting preferably of an arcuate plate. 'I'he method of. securing the surface coating is'to suspend the heated base plate in a concentrated solution of ammonia in which colloidal graphite is in suspension. 'Ihere is then deposited on the copper oxide plate a layer of graphite and cuprous amino-oxide; the coated plate is then raised to a temperature at which the ammonia is volatilized and a hard coating of deilocculated graphite firmly adheres to the compound base. One advantage of this treatment lies in the uniform thickness of the resistance coating, or graphite layer;

A suitable movable contact may be provided for a variable resistance device. Otherwise, the

` 'pression springs to insure uniform contact betwo contact members may remain stationary. By varying the thickness of the graphite coating, the degree of resistance oiered by the element may be xed.

Reference to the accompanying drawing will assist in understanding the invention. In the drawing Fig. l diagrammatically shows a plan view of the device, Fig. 2 a cross section at 2-"'2 and Fig. 3 a cross section of the resistance element. w

In the drawing 1 represents the cuprous oxide graphite coated resistance element, 2 the insulator .base to which it is attached and 3 and 4 the terminals of the resistance plate. At 5 is an arm rotatable on shaft 'I and carrying contact plate 6, in contact with the resistance plate l. At 9 is a head attached to shaft 7 for rotating the arm 5, 10 being a nut lock and 11 'representing comtween contact bar 6 and resistance plate 1.

Fig. 3 shows the arch constructioniof resistance element 1. Y

, 1931, Serial No. 513,083

has also been determined that if the temperan ture is raised beyond about 400 C. the resistance of the element increases materially. Thus for lower resistance .the element should be heated to between 350 and 400 C. which permits the use of a minimum thickness of graphite coating. Measuring one sample of this device it is found that without the application of heat it had a resistance of about 15,000 ohms after being dipped in a solution containing 5% of solid graphite; but after heating to 350-C. the resistance dropped to 500 ohms.

In the heating process a cuprous amino-oxide is formed by the reaction of the strong ammonia with the cuprous oxide surface. This compound is very effective as a binder, causinga strong adherence between the hard graphite layer and the surface of the base element.

What I claim is:

1. A resistance element comprising a base of a crystalline compound of the class comprising the electronically conductive oxides, sulphides, selenides, and tellurides, having a lower resistance surface comprising the reaction product of an ammonia-graphite mixture with the base material.

2. A resistance element comprising a base of a. crystalline compound of the class comprising the electronically conductive oxides, sulphides,

selenides, and tellurides, having a lower resistance surface comprising the reaction product of an, ammonia-graphite mixture heated with the base material.

3. A variable resistance element comprising a base of a crystalline compoun'dof the class comprising the electronically conductive oxides, sulphides, selenides,- and tellurides, having a lower prising the reaction vproduct of anammoniagraphite mixture with the base material.

5. A variable resistance element comprising a,

base composed of copper oxide having a lower c 5 resistance surface comprising the( reaction prod- `uct of an ammoniabase material.

graphite mixture with the which colloidal graphite is suspended, heating said plate until the ammonia graphite mixture combines with the copper oxide.

SAMUEL RUBEN. 

